Study of Cosmic Ray Origin andTransient Sources with CTA(subtext: why we need LSTs in the South)
Susumu Inoue (RIKEN)
on behalf of many collaborators inside/outside CTA

outline
1. introduction- CTA and LSTs
- importance of LSTs in the South
2. cosmic ray (CR) origin
a. Galactic CRs- supernova remnants (SNRs): CR acceleration and escapeb. ultra-high-energy CRs (UHECRs)- active galactic nuclei (AGN) jets: role of Centaurus A
3. transient sources(- short gamma-ray bursts (GRBs) and gravitational waves)- blazar flares and neutrinos- radio, optical transients

CTA sensitivity (steady sources)

LSTs

20-100 GeV

transition regime from space to ground facilities-> currently some sensitivity gap

CTA vs Fermi-LAT for transient/variable sources- sensitivity for short exposure times (~effective area)
greater than satellites by several orders of magnitude- rapid slewing for LSTs (180 deg in 20 sec)

extragalactic gamma-ray horizon vs redshiftτγγ=1: Baseline
Y. Inoue, SI+ 2003
τγγ=5: Baseline
ApJ 768, 197
τγγ=1: Lower-Pop-III

104

Energy (GeV)

gamma-ray energy where tgg=1

l Journal, 768:197 (17pp), 2013 May 10τγγ=1: Upper-Pop-III
Kneiske+’04 (τγγ=1)
Franceschini+’08 (τγγ=1)
Finke+’10 (τγγ=1)
Gilmore+’12 (τγγ=1)
S.Inoue+’10 (τγγ=1)
Obs. Max. Energy

3

10

22
102

20
18

101
0.02

16

5

6

7

8

9

z~1-6

10

0.1

1

10

Redshift z

LSTs crucial for high-z extragalactic transients

ray horizon energy where τγ γ = 1. The baseline, lower-Pop-III, and upper-Pop-III models are shown by the thick solid,
ctively. The dashed, dotted, dot-dashed, double dot-dashed, triple dot-dashed curves represent the models by Kneiske et

CTA vs current Cherenkov telescopes for transients- all-sky coverage with North and South sites- versatile pointing (sub-arrays, divergent pointing)- real-time analysis (alerts issued in ~30 sec)

Physics 67 (2015) 33–46

Divergent
pointingwith CTA
Divergent
pointingwith CTA

Lucie GL

Normalmodepointing mode
Normal pointing

10

5

5
0

0

-5

-5

-10

-10

Szanecki+ 2015

-15
-15

-15
-10
-15

normal
-5-10

0 -5

50

800

800

700

700

600

600

500

500

400

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100

0
10 5
1510
15
[degree] [degree]

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-5

-5

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100

-10

-10

50

50

-15
-15

-15
-10
-15

15
10

[degree]1015[degree][degree][degree]divergent pointing
for MSTs/SSTs
15

pointing mode
Divergent Divergent
pointing mode

divergent
-5-10

0 -5

5 0

0
10 5
15 10
15
[degree] [degree]

FoV ~20 deg dia.

Gérard+ 2015

0

4: Gamma-ray
acceptanceafter directionand energy
reconstruction
cuts. The
total
numberof e
Figure4: Gamma-ray
acceptanceafter directionand energy
reconstruction
cuts.
The
total numbwider FoV Figureatexpenseofangular/energy
resolution
passing
those cuts
469are051
for051
thefornormalmode and447
918447
for918the fordivergentmode. mode.
passing
thosearecuts
469
the normalmode
andthe divergent- fast scanning of large regions, e.g. GW follow-up- transient survey?
1

.U.]

1

.U.]

1

.U.]

.U.]

Fig. 1. Three modes of configuration of the telescope system used in the sky-survey
scans: (a) normal (parallel) mode; (b) divergent mode; (c) convergent mode.

1

importance of Southern sky / all-sky coverage
unique targets in Southern sky- Galactic Center- inner Galactic plane (majority of Galactic objects )- Magellanic Clouds- Centaurus A (nearest active galaxy + radio galaxy)unique facilities (transient factories) in Southern hemisphere- radio: SKA and its pathfinders (ASKAP, MWA, MeerKAT...)- optical: LSST
- neutrinos at extremely high energy: IceCube
all sky coverage- potentially unique transients (“Rosetta Stone” events)
c.f. SN 1987A, GW170817...

2. cosmic ray origin
observed spectrum of cosmic rays
up to knee (<1015-16 eV)
Galactic SNRs?
likely, but not yet definitiveknee-ankle (1015-16-1018 eV)
Galactic? no new source?

knee

ankle
Gaisser 05

toeabove ankle (>1018 eV)extragalactic: AGNs?
GRBs?

the maximum likelihood analysis, as mentioned
above. With this treatment, the measured fluxes
below 1 GeV contain small contributions fromthe escaped cosmic rays, but this does not affectour conclusions. The escaped cosmic rays may
significantly contribute to the measured TeV fluxes
from IC 443 (29, 30). Emission models could be
more complicated. For example, the cosmic-ray

ray emission. Unless we introduce in an ad hoc
way an additional abrupt break in the electron
spectrum at 300 MeV c−1 (Fig. 2, dash-dottedlines), the bremsstrahlung models do not fit theobserved gamma-ray spectra. If we assume thatthe same electrons are responsible for the observed synchrotron radiation in the radio band,a low-energy break is not expected to be very

Galactic CRs: supernova remnant (SNR) paradigm- consistent energetics

LGCR~1041 erg/s~0.1xESN/tSN

Table 1. Spectral parameters in the energy range of 60 MeV to 2 GeV for power-law (PL) and- plausible theory of
broken power-law (BPL) models. TS = 2 ln(L /L ) is the test-statistic value.
diffusive shock accelerationModel
K (cm s MeV )GGe (MeV)TS
IC 443- observational evidence PL
11.7 (T0.2) × 10
1.76 T 0.02——
21,651BPL
11.9 (T0.6) × 10
0.57 T 0.25
1.95
245
22,010
W44
radio+X-ray: electron acceleration
PL
13.0 (T0.4) × 10
1.71 T 0.03
—
—
6,920
BPL
15.8
(T1.0)
×
10
0.07
T
0.4
2.08
253
7,351
GeV(-TeV): proton acceleration
1

2

−1

−1

0

1

2

br

−10
−10

+0.02
−0.02

+16
−15

+0.03
−0.03

+11
−11

−10

W44

1049

10-9

IC 443
1048

10-10

10-11

1047

Fermi Col. 13
Fitted π0 decay model

10-12

1046

Derived Proton spectrum
VERITAS (30)
MAGIC (29)

Cas A Chandra

108

109

1010
Energy (eV)

1011

1012

Proton Spectrum E2 dN/dE (erg)Gamma-ray flux E2 dN/dE (erg cm-2 s-1)

−10

issues for the SNR paradigm:
acceleration to PeV, CR escapefrom Uchiyama

from S. Funk
mid-ageyoung- no evidence yet for accelerators up to knee energy (Pevatrons)
non-SNR sources (black holes, pulsars, ...)?
-> search featuring SSTs
- potential evidence for time- and energy-dependent CR escape-> clarify including South LSTsUHECR sources: accelerationfrom“Hillas plot” adapted
Yoshida & Dai 98

E ≦ Ze B R (v/c)
confinement

magnetars

Emax acceleration vs:
B

GRBs
B~∝R-1

escapesource lifetime
adiab. expansion loss
radiative loss

AGN jetsclustersR

old favorite: AGN jets
leading contender: GRBs
dark horse: magnetars
clusters, etc.

AGN: acceleration sites
low power (FR 1) radio galaxy

near-nucleus
highest E not expected
e.g. Szabo & Protheroe 94

inner jet (blazar)
Emax~Epg~<1020eV
accel./escape nontrivial
e.g. Mannheim 93

diffuse lobe?
c.f. diffuse GeV from
Cen A, Fermi bubble

from Chandra webpage

Centaurus A- nearest AGN by far (D~3-5 Mpc)
- low power (P2.7~2x1024 W/Hz)- inner lobes (~10 kpc); active- outer lobes (650 kpc); “inactive”?

1kpc

Morganti+ 99

1D-projection of the event map

Fig. 1. (A and B) FermiLAT g-ray (>200 MeV)
counts maps centeredon Cen A, displayed withsquare-root scaling. In
both (A) and (B), modelsof the galactic and isotropic emission components were subtracted
from the data (in contrast to the observedcounts profile presented
in Fig. 2). The images
are shown before (A)19, A71 (2018)and after (B) additional subtraction of field
point sources (SOM) and⇥are shown adaptivelyissmoothed with a minimum signal-to-noise ratiod,of 10. In (B), the whitehecircle with a diameter of
at1° is approximately thescale of the LAT point-spread function width. (C) For comparison, the 22-GHz radio map
hefrom the 5-year WMAP data set (8) with a resolution of 0°.83 is shown. J2000, equinox; h,rehour; m, minutes.

Cen A
Preliminary- diffuse
GeV associated with outer lobe
VLA

- 2 component GeV+TeV associatedwith “core” (includes inner lobe)- spatial extension of “core” TeV
along jet direction? H.E.S.S.
-> need South LSTs Preliminary

Fermi Col. 10

Projection along
the radiojets
2-zoneSSC
fit• Minor axis: no extension
HESS Col. 18• Major axis: PSF folded with thebest-fit width from the 2D fit

hadronic modeling also possible
Cerruti+ 1610.00255

Fig. 3. SED of Cen A core with model fits as described in text. The
red curve corresponds to an SSC component designed to fit the radio
Berlincorresponds to a second SSC comto sub-GeV data.TeVPA
The 2018,
blue curve

Sanchez+(HESS), TeVPA 2018 11
D. Sanchez

nloaded from www.sciencemag.org on May 6, 2010

ot
he
dex
nd
nd
pe
in
as
w
nt
ue

Cen A in gamma-rays

Cen A in UHECRs?
- potential correlation with
Auger “warm” spot

Moskalenko+
09

vs other nearby radio galaxies

van Velzen+ 12

all radio galaxies z<0.03
circle area proportional to radio flux

name
Cen A
M87
For A
UGC 7360
NGC 4696
NGC 5090
I 4296
NGC 6328
NGC 11294
2MASX

D[Mpc]
3.6
18
21
32
42
47
51
59
67
69

3. Transient Sources: Gamma-Ray Bursts
Most luminous explosions
in the Universe,
largely unexplored at VHE

via VHE observations:
Clarify physics of GRBs
- mechanisms of prompt and early afterglow radiation,
particle acceleration, jet formation
Probe the Universe- extragalactic background light (deeper than AGN)
- intergalactic magnetic fields
Test UHECR origin,fundamental physics
search forsignatures of:- accelerated hadrons- Lorentz invarianceviolation

Piran 03

first clear detection of a GRB in VHE gamma rays:>20s above 300 GeV
GRB 190114C by MAGIC

Papers in preparation, please stay tuned!

New window onto the Universe,
turned new mystery- clear indicators of VHE/UHE cosmic ray production- being detected by IceCube, but no correlation withpromising sources (bright GRBs, bright blazars) until recently
VHE g follow-up
identify via co-produced g rays (either leptonic or hadronic):- neutrino sources (if g-rays escape + propagate)- VHE/UHECR sources (if g-rays + CRs escape+propagate)high-energy neutrinos

t energies below 100 TeV,
eply with energy, allowing
s to be more easily identis. The muon-neutrino as-参照

31 October 2017. Although no additional excess
of neutrinos was found from the direction of TXS
0506+056 near the time of the alert, there areindications at the 3s level of high-energy neutrinon / EM observations of IC-170922A / TXS 0506+056

IceCube- 56.5% probability of
being astrophysical n
今回のフェルミ衛星によるガンマ線観測結- alert after 43s- well localized, <<1 deg
ewu- En~290
TeV
m f f(183 TeV - 4.3 PeVf
90% C.L.
C + , +,
assumingà* -2.13 spectrum)
Fermi-LAT- coincident
C with+ ,blazar+, TXS 0506+056
10 )in bright(2008stated(0.5 2017
yr-long)
1il- significance of association ~3s-> possible source of possible
astrophysical high-energy neutrino
MAGIC
Fermi-LAT~6s detection >~100 GeV

withondingotal
800 photoelectrons. Inset is an overhead perspective view of the event. The best-fitting track direction is shown as an arrow,h angle 5:7þ0:50"0:30 degrees below the horizon.

Downloaded from http://science.sciencemag.org/ on July 12, 2018or
bewhich al isf the hit,iest hitsimes
he first
he tracklier andwith thest andy. Theok to3000 ns.
phere isarithm(14), was reported to be 56.5% (17). Although
IceCube can robustly identify astrophysical neutrinos at PeV energies, for individual neutrinos
at several hundred TeV, an atmospheric origin

IceCube, Fermi, MAGIC+, 2018, Science 361, eaat1378 ]MAGIC observations of IceCube-170922A’s

pixel, using detected photons with energy of 1 to 300 GeV in a 2° by 2°

VHE observations of TXS 0506+056
crucial contraints on physical conditions of source- <day timescale flaring -> constraints on size of emission region
IC-170922A

flux

time

energy flux

- prominent steepening of
g-ray spectrum at ~100 GeV-> consistent with internal
gg absorption with UV-X-rays= main targets for pg
neutrino production
MAGIC Col. arXiv:1807.04300

Fermi-LAT
G~-2.0MAGIC
G~-3.5 - -4.0

energyissues for high-energy neutrino origin
questions- plausibility of 1-zone interpretation of EM data + IC-170922A- origin of 2014-2015 neutrino flare during low gamma-ray state (if real)- relation to other blazars: why TXS 0506+056 and not others?
high-frequency BL Lac objects, e.g. Mrk 421
flat spectrum radio quasars, e.g. 3C279- contribution to diffuse IceCube flux -> likely minor- origin of dominant source(s) of diffuse IceCube flux…
outlookmore neutrino+EM observations necessary- X-rays for constraining cascade emission- VHE for constraining pg target density via gg absorption -> CTA- extremely high-energy neutrinos for clarifying UHECR origin

The Astrophysical Journal, 835:151 (15pp), 2017 February 1

IceCube sensitivity: North vs SouthTo ﬁndunbinned lsky. This
spaced poindowngoing
IceCubereconstruct
Col.
2017 in Equation
Thus, fo
ApJ 835, 151
test statistic
upgoingvalue deﬁnhorizontal
backgroundsky separat
energy reac
the full-sky
for the cha- sub-PeV
sensitivity:> SouthFigure5. Discovery
potential (5σ) Northfor this analysis
in different bins of neutrino-2
position inE
withhalf-decade
width.
Withinthisenergyrange,
anspectrumenergyE
νn- PeV-EeV sensitivity: North < South, horizontal
log10 p tha
is used. Three different declinations are shown: up-going (red, δ = 60°),-> Southof EHE
horizontal(blue, LSTs
δ = 0°), forand follow-up
down-going (yellow,
δ =neutrinos−60°) events. For
independen
down-going events, the dashed line shows the discovery potential not using theJean-Pierre Macquart

radio transients

Pietka+ 15, Macquart+ 1515

10

AGN/Blazar/QSO
K

Fast Radio Bursts
8

GRBs

10

0

10

Pulsar GRPs
Crab ns

Supernovae

Keane Burst
RRATs

GCRT 1745

10 4
K

105

Uncertainty Principle2

Gpc

In Coh10 2
co0
he ereK
re nt
n t Em
Em is
i ss si o n
io
n
10 1
2
K

10 2

10

Lpeak (Jy.kpc )peak luminosity normalized at D=kpc

Fast Radio Burst Science

Novae
X-ray Binaries

Pulsarskpc

Solar Bursts

RSCVn

10-5

10-10 -10
10

- Parkes- SKA1-LOW- SKA1-MID Jupiter DAM
10-5

Flare Stars/Brown Dwarves100ν.W (GHz.s)

5

10

1010

obs. frequency x duration- e.g.
fastradio
bursts:(z~0.2-3),
mysterious
Figure3: Transientparameter
space ofextragal.
specific luminosity
versus the productotherwiseof observing frequency
andtransient duration. All the known sources of transient radio emission are shown. e.g.
Overplotted
are 1 kpc andMurase+16
somepredictions
for
GeV-TeV
emission
1 Gpc sensitivity curves for Parkes (black), SKA1-LOW (pink) and SKA1-MID (grey). This figure illustrates
the depth LSTs
to which SKA1
probe the transientradio sky.
For example
published
FRBs are all just above- South
forcansynergy
withSKA
andthe its
pathfinders
the Parkes 1 Gpc sensitivity limit (black line). These sensitivity limit curves are for beamformed searches.

58

optical transients

S. R. Kulkarni

Kulkarni 1202.2381- e.g. supernova shock breakout events
some predictions for GeV-TeV, n emission- South LSTs for synergy with LSST

Figure 2. Theoretical and physically plausible possibilities are marked in the explosive transientphase space. The original figure is from Rau et al. (2009). The updated figure
show thee.g. (toKashiyama+
13
unexplored sub-day phase space) is from the LSST Science Book (v2.0).

summary- LSTs crucial for studying:- extragalactic transients- GeV-TeV crossover regime of space and ground instruments- necessary in South for studying:- Galactic CR sources, promising UHECR source- all-sky coverage of transients- Galactic CR origin: SNR paradigm working
except for Pevatrons, CR escape process -> S-LSTs- UHECR origin: mysterious
Cen A: unique g-ray source, promising UHECR source-> study including S-LSTs- transients- GRBs: great prospects- neutrinos: search initiated but still mysterious-> S-LSTs to follow-up EHE neutrinos (~UHECR accel.)- radio, optical -> S-LSTs for synergy with premier facilities